1. Field of the Invention
The present invention relates to a liquid discharge head for performing recording on a recording medium by, for example, discharging liquid such as ink and to a method of manufacturing the liquid discharge head. In particular, the invention relates to a liquid discharge head for performing inkjet recording.
2. Description of the Related Art
Inkjet recording heads are examples of liquid discharge heads that are generally known.
Referring to FIGS. 8A to 8C, a structure of an inkjet recording head is briefly described.
As illustrated in FIG. 8A, an inkjet recording head H1001 includes a tank holder unit H1003 and a recording element unit H1002 for discharging ink.
Ink is supplied from an ink tank (not illustrated) to the recording element unit H1002 through an ink flow path formed in the tank holder unit H1003.
The ink flow path is formed in the tank holder unit H1003 by joining a tank holder H1500 illustrated in FIG. 8B to a flow path plate H1600 illustrated in FIG. 8C.
Known methods for joining the tank holder H1500 to the flow path forming plate H1600 include ultrasonic welding (Japanese Patent Laid-Open No. 2007-283668) and laser welding (Japanese Patent Laid-Open No. 2005-096422).
Among the two methods, the laser welding method will be described.
The term “laser welding” generally refers to a method of making a member that is transparent to a laser beam and a member that is capable of absorbing a laser beam contact each other and irradiating a region to be welded with a laser beam so as to join the members together.
As compared with ultrasonic welding, laser welding has an advantage in that foreign matter is negligibly generated at the welded portion and is used as effective means for forming an ink flow path.
Referring to FIGS. 9A to 9C and FIGS. 10A to 10C, which are schematic sectional views of the recording head illustrated in FIGS. 9A to 9C, a method of joining a tank holder H1500 to a flow path forming plate H1600 by laser welding described in Japanese Patent Laid-Open No. 2005-096422 will be described.
The tank holder H1500, which is capable of absorbing a laser beam, and the flow path forming plate H1600, which is transparent to a laser beam, are made to contact each other using a press jig 510 (FIGS. 9A and 10A). Subsequently, while the tank holder H1500 and the flow path forming plate H1600 are in contact with each other, a contact surface 600 is irradiated with a laser beam (FIGS. 9B and 10B) so that weld portions 610 are formed and thereby an ink flow path H1601 is formed (FIG. 10C).
In general, examples of laser irradiation methods include a scanning method, which is described in Japanese Patent Laid-Open No. 2005-096422, and a simultaneous irradiation method.
With the scanning method, a desired welding region H1602 is irradiated with a laser beam along a path in the welding region H1602 (see FIGS. 8B and 8C) in a scanning manner by focusing the laser beam to a small spot, the laser beam being emitted from a laser beam irradiation apparatus 500 as illustrated in FIGS. 9B and 10B.
With the simultaneous irradiation method, a desired welding region is irradiated with a laser beam in one go.
The ink flow path has a fine structure and the welding region is very small. In such a case, the scanning method and the simultaneous irradiation method have the following situations.
The scanning method has a situation in that a very long time is required to focus the laser beam on a desired path in a very small welding region, scan the region along the path, and weld the region.
For example, as illustrated in FIGS. 8B and 8C, the desired welding region H1602 and an ink flow path H1601 of the inkjet recording head have fine structures with very small widths. Thus, irradiating areas excluding the ink flow path H1601 as illustrated in FIG. 10B is extremely time-consuming. Therefore, the scanning method is not suitable for manufacturing a large number of inkjet recording heads.
In contrast, with the simultaneous irradiation method, the time required for welding can be reduced. However, when a welding region has a fine structure, providing a mask on a portion corresponding to a fine ink flow path and irradiating only the welding region with a laser beam is difficult.
Referring to FIGS. 11A to 11C, the simultaneous irradiation method for welding the tank holder H1500 and the flow path plate H1600 will be described. As illustrated in FIG. 11B, both the contact surface 600 and a region to become the ink flow path H1601 are simultaneously irradiated with a laser beam so that weld portions 610 are formed. As a result, as illustrated in FIG. 11C, a damaged portion 620 may be formed on a surface of the ink flow path H1601 by the laser beam.
If the damaged portion 620 is generated in the ink flow path H1601, the damaged portion 620 may impede the flow of ink and may impair the reliability of the inkjet recording head H1001.